Being self-employed means dealing with income tax and National Insurance through Self Assessment, often making advance payments on account toward next year's bill. This calculator brings all those figures together in one place for 2025/26 — from gross turnover through to net take-home after tax, and a projected payment schedule for the following year.
2025/26 Key Self-Employment Tax Rates
- Personal Allowance: £12,570
- Basic rate income tax (20%): £12,571–£50,270
- Higher rate income tax (40%): £50,271–£125,140
- Additional rate (45%): above £125,140
- Class 4 NI: 6% (£12,570–£50,270); 2% above £50,270
- Class 2 NI: Abolished April 2024
- Annual Investment Allowance: £1,000,000
Self-Employment Tax Summary Calculator
How Self-Employment Tax Is Calculated
Self-employed individuals are taxed on their annual trading profit, calculated as turnover minus allowable expenses and capital allowances. This profit is then combined with any other income to give total income. Personal pension contributions and Gift Aid donations are deducted to arrive at adjusted net income (ANI), which is the figure used for income tax calculations.
Income tax is charged on ANI above the personal allowance using the standard bands. Class 4 NI is charged separately on self-employment profits only (not other income), at 6% on profits between the Lower Profits Limit (£12,570) and the Upper Profits Limit (£50,270), and 2% above.
Capital Allowances and the AIA
Capital allowances let you deduct the cost of business assets against your profit. The Annual Investment Allowance (AIA) lets you deduct the full cost of qualifying plant and machinery up to £1 million in the year of purchase — effectively 100% first-year relief. For assets not covered by AIA, the Writing Down Allowance (WDA) typically applies at 18% per year for the main pool or 6% for the special rate pool.
Claiming capital allowances reduces your taxable profit and therefore both your income tax and Class 4 NI bills. They are particularly valuable for higher-rate taxpayers where each pound of relief saves 40p in income tax plus 2p in Class 4 NI.
Payments on Account Explained
Payments on account are advance payments toward your Self Assessment bill. They are required when your prior year's Self Assessment liability (income tax plus Class 4 NI) was £1,000 or more and less than 80% was collected at source. Each instalment is 50% of the prior year's liability.
POA 1 is due 31 January. POA 2 is due 31 July. A balancing payment (or refund) is made by the following 31 January once the actual tax for the year is known. If your income has risen significantly, the balancing payment plus the new POA 1 can create a large combined bill in January.
You can apply to reduce payments on account if you expect your income to be lower than the prior year. However, if you reduce them too much and the actual tax is higher, HMRC will charge interest on the underpayment.
Pension Contributions and Tax Efficiency
Gross personal pension contributions reduce your adjusted net income for income tax purposes. If your ANI is between £50,270 and £100,000, contributions can move income into the basic rate band and save 40% tax on the amount contributed. Near the £100,000 threshold, contributions preserve the personal allowance and effectively create a 60% relief in that band.
Pension contributions do not reduce Class 4 NI, which is based on trading profits. For NI efficiency, employer contributions through a limited company structure are more tax-efficient, but this requires operating through a company rather than as a sole trader.
Frequently Asked Questions
Income tax on taxable profit above the personal allowance, and Class 4 NI on profits above £12,570. Class 2 NI was abolished from April 2024.
Payments on account are advance payments toward next year's tax bill. Each payment is 50% of the prior year's Self Assessment liability (income tax + Class 4 NI). POA 1 is due 31 January and POA 2 is due 31 July.
Net profit = turnover minus allowable business expenses minus capital allowances. Allowable expenses include things like professional fees, office costs, travel, and business insurance.
Gross personal pension contributions reduce adjusted net income for income tax. They do not reduce Class 4 NI. They can save significant income tax for higher-rate taxpayers and help preserve the personal allowance near £100,000.
A balancing payment is the remaining tax due after payments on account are credited. It is paid by 31 January following the end of the tax year. If actual tax is less than what was paid on account, HMRC issues a refund.
Yes. You can apply to HMRC to reduce POAs if you expect a lower income than the prior year. If you reduce them incorrectly and the actual tax is higher, HMRC will charge interest on the shortfall.
At £45,000 profit, effective combined rate (income tax + Class 4 NI) is around 25–28%. At £60,000 it is higher due to the 40% income tax rate. The calculator shows your exact effective rate.
Gross Gift Aid donations reduce adjusted net income in the same way as pension contributions, potentially saving higher-rate income tax and preserving the personal allowance.
Yes, for most business equipment. The Annual Investment Allowance allows you to deduct the full cost of qualifying plant and machinery in the year of purchase, up to £1 million per year.
You must register for VAT if your taxable turnover exceeds £90,000 in a rolling 12-month period (2025/26 threshold). Registration is optional below this level but may be beneficial if your clients are VAT-registered businesses.
Yes. Student loan repayments are calculated on income above the repayment threshold and included in your Self Assessment return, covering self-employment profits.
If you are self-employed with annual profits over £1,000, you must register by 5 October following the tax year end. The online return deadline is 31 January. Late filing attracts a £100 penalty plus further daily charges.